Methyl chloroform stabilized with monohydroxy alkanoic acids and esters



United States Patent 3,336,234 METHYL CHLOROFORM STABILIZED WITH MONOHYDROXY ALKANOIC ACIDS AND ESTERS James Holmes Speight, Widnes, England, assignor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Filed Apr. 20, 1964, Ser. No. 361,280 Claims priority, application Great Britain, May 1, 1963,

17,219/63 9 Claims. (Cl. 252-171) This invention relates to a stabilized solvent, more particularly to methyl chloroform (1,1,1-trichloroethane) stabilized against metal-catalysed decomposition.

Chlorinated hydrocarbons are widely used as solvents for metal degreasing operations, and a variety of stabilizers have been proposed for use in preventing decomposition of the solvent and corrosion of metals in contact with solvent. Methyl chloroform is very effective for many applications, for example for the removal of grease from metals in the cold, but has a greater tendency to decompose than the commoner solvents such as trichloroethylene and tetrachloroethylene.

Consequently, many of the materials which function quite adequately as stabilizers in other solvents provide only short-term stabilization of methyl chloroform. Some metals are more readily attacked than others, and it is very desirable that the solvent should be sufficiently stabilized to withstand prolonged contact with these very active metals or alloys even though, in use, such active metals may make up only a small proportion of the metal normally expected to be in contact with the solvent.

I have now found that efficient stabilization of methyl chloroform can be achieved by addition of a hydroxy acid and/or a hydroxy ester. I have also found that a nitroalkane used in conjunction with an aliphatic hydroxy acid and/or an aliphatic hydroxy ester enhances the stabilizing action still further.

Thus according to the present invention I provide a stabilized 1,1,1-trichloroethane composition which comprises l,l,l-trichloroethane together with a minor proportion of an aliphatic hydroxy acid and/ or an alkyl ester of an aliphatic hydroxy acid and preferably also a minor proportion of a nitroalkane.

The hydroxy acids, hydroxy esters and nitroalkanes do not react with the oil, grease and fatty compounds present on the surface of the articles which are commonly degreased in chlorinated hydrocarbon solvents and are therefore suitable for continuous use as stabilizers in methyl chloroform.

Suitable hydroxy acids include aliphatic hydroxy acids containing up to 4 carbon atoms in the molecule, for example alpha-hpdroxyisobutyric acid. Suitable hydroxy esters include the methyl and ethyl esters of the said aliphatic hydroxy acid, for example methyl alpha-hydroxyisobutyrate.

Suitable nitroalkanes include nitromethane, nitroethane, l-nitropropane and 2-nitropropane. Mixtures of the said nitroalkanes may also be used if desired. In general, proportions of nitroalkane between 0.5% and 2% by weight of the methyl chloroform are very suitable.

Proportions of the hydroxy acid or hydroxy ester between 0.5% and 6%, preferably between 1% and 4%, by weight of the methyl chloroform may be used. For effective stabilization, the proportions of the hydroxy acid and/or ester and of the nitroalkane to be used may be found to vary somewhat according to the particular stabilizers employed and the particular conditions of use, for example the particular metals to be in contact with the solvent. Smaller amounts than those indicated may provide a stabilizing effect, but in commercial practice it is advisable to keep the proportions above the minimum values given in order to provide an adequate margin of safety. Proportions greater than those in the ranges given above may be used if desired, but little additional stabilization is thereby achieved.

It must be understood that the stabilizers of the present invention may furthermore be used in conjunction with conventional stabilizing systems. For example it is known that decomposition of chlorinated hydrocarbons can occur by oxidation under the influence of light and heat, with the development of acidity, and it has been proposed to inhibit this type of decomposition or to remove the acidity as it is formed by the use of various additives, for instance antioxidants and acid acceptors. Accordingly, when the stabilizers of the present invention are incorporated in chlorinated hydrocarbons to inhibit the metalcatalysed decomposition,conventional preservatives may also be present if desired.

The invention is illustrated but not limited by the following examples in which the parts and percentages are by weight.

Example 1 400 parts of a methyl chloroform composition containing as stabilizer 12 parts of methyl alpha-hydroxyisobutyrate were boiled under reflux in glass apparatus with 40 parts of an aluminum alloy known in commerce as M10 (cast 3/60 silicon) in the form of swarf. The methyl chloroform was converted into a tar only after refluxing for hours.

By way of comparison the procedure was repeated using methyl chloroform containing no added stabilizer. A vigorous reaction occurred as soon as refluxing commenced and the methyl chloroform was rapidly converted into a tar.

Example 2 400 parts of a methyl chloroform composition containing 12 parts of methyl alpha-hydroxyisobutyrate together with 4 parts of nitroethane were boiled under reflux in glass apparatus with 40 parts of aluminum alloy M10 in the form of swarf. No reaction was evident after refluxing had been continued for 350 hours.

By way of comparison this procedure was repeated using 400 parts of methyl chloroform containing 4 parts of nitroethane as the only added stabilizer. The vigorous reaction occurred after refluxing for only 5 hours.

Example 3 To 400 parts of methyl chloroform were added 12 parts of alhpa-hydroxyisobutyric acid and the mixture was boiled under reflux in glass apparatus with 40 parts of aluminum alloy M10 in the form of swarf. The vigorous reaction did not occur until refluxing had been continued for 750 hours.

What I claim is:

1. A stabilized 1,1,1-trichloroethane composition which comprises 1,1,1-trichloroethane together with a stabilizing amount of a stabilizer selected from the group consisting of monohydroxy alkanoic acids containing up to four carbon atoms and alkyl esters of said acids.

2. A composition as claimed in claim 1 wherein said stabilizer is alpha-hydroxyisobutyric acid.

3. A composition as claimed in claim 1 wherein said stabilizer is the methyl or ethyl ester.

4. A composition as claimed in claim 1 wherein said stabilizer is the methyl ester of alpha-hydroxyisobutyric acid.

5. A composition as claimed in claim 1 which also contains a stabilizing amount of a nitroalkane containing up to three carbon atoms per molecule.

6. A composition as claimed in claim 5 wherein the proportion of nitroalkane is between 0.5% and 2% by weight of the 1,1,1-trichloroethane.

7. A composition as claimed in claim 1 wherein the total proportion of said stabilizer is between 0.5% and 6% by weight of the 1,1,1-trichloroethane.

8. In a method for degreasing metal with 1,1,1-trichloroethane, the improvement which comprises degreasing said metal with 1,1,1-trichloroethane containing a stabilizing amount of a stabilizer selected from the group consisting of monohydroxy alkanoic acids containing up to four carbon atoms and alkyl esters of said acids.

9. A method according to claim 8 wherein said metal is aluminum.

4 References Cited UNITED STATES PATENTS 2,595,636 5/1952 Brighton et a1. 260652.5 X 2,958,712 11/1960 Starks 260652.5 3,060,125 10/1962 Sims 260-6525 X FOREIGN PATENTS 234,561 7/1961 Australia.

LEON ZITVER, Primary Examiner.

M. JACOBS, Assistant Examiner. 

8. IN A METHOD FOR DEGREASING METAL WITH 1,1, 1ITRICHLOROETHANE, THE IMPROVEMENT WHICH COMPRISES DEGREASING SAID METAL WITH 1,1,1-TRICHLOROETHANE CONTAINING A STABILIZING AMOUNT OF A STABILIZER SELECTED FROM THE GROUP CONSISTING OF MONOHYDROXY ALKANOIC ACIDS CONTAINING UP TO FOUR CARBON ATOMS AND ALKYL ESTERS OF SAID ACIDS. 